Conversion of wavelengths from one part of the electromagnetic spectrum to another part of the spectrum typically involves a system using a nonlinear crystal and the mechanism of sum-frequency-generation (SFG). The SFG occurs in the interaction between an incoming laser beam to be wavelength converted and an intensive laser beam, resulting in an output laser beam having a wavelength corresponding to the sum of the frequencies of the interacting laser beams. Thereby, the wavelength of one of the incoming laser has been up-converted to a higher frequency/shorter wavelength.
Examples of such systems are described in WO 2010/006985 or in EP 0 725 307.